Doc: improve documentation about exponentiation operator.

Now that we're not having to wedge this into the straitjacket of
the old operator table format, we can add another example to
clarify the point about left-to-right associativity.

Per suggestion from mdione at grulic.org.ar.

https://postgr.es/m/162661954599.693.13700316547731859171@wrigleys.postgresql.org

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 5dea1aa986e74d26a78feaf45209a8676ff7225c..32328de46d5f410ab275a53708c290c745a89816 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1007,16 +1007,23 @@ repeat('Pg', 4) PgPgPgPg
         double precision
        
        
-        Exponentiation (unlike typical mathematical practice, multiple uses of
-        ^ will associate left to right)
+        Exponentiation
        
        
         2 ^ 3
         8
        
+       
+        Unlike typical mathematical practice, multiple uses of
+        ^ will associate left to right by default:
+       
        
         2 ^ 3 ^ 3
         512
+       
+       
+        2 ^ (3 ^ 3)
+        134217728